In a bowl, combine the crabmeat, mayonnaise, celery, onion, mustard and seasonings. Spread 1/2 cup crab mixture on the bottom of each roll. Sprinkle with cheese. Spread butter on cut side of roll tops. Broil both halves of sandwiches 4 in. from the heat for 3-4 minutes or until cheese is melted and crab mixture is bubbly.